Delay powder



Patented Get. 12, 1948 UNITED STATES ENT 0 F Fl CE No Drawing.Application May 5, 1944, Serial No. 534,289

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370O'. G. 757) 13 Claims.

The invention described herein may be manufactured and used by or forthe Government for governmental purposes, without the payment to me ofany royalty thereon.

This invention relates to delay powders for use in fuzes of varioustypes, the powders being an improvement on the type of powder disclosedin my prior Patent No. 1,877,127, dated September 13, 1932.

In the patent cited delay powders were described comprising a metallicchromate, a metal adapted to react with oxygen to form a solid, and abinder. Such powders have found extensive use for various purposes,particularly in closed systems where the development of gaseous productsof combustion b a delay powder would be objectionable if notdefinitelyprohibitive. Owing to the special property of such powders to producelittle or no gas upon combustion, new demands have arisen in connectionwith their application, such demands making necessary powders having amuch slower rate of burning than is obtainable with the type formerlydeveloped. The reason thatthe chromate-metal powders cannot be adjustedby altering the proportion of the ingredients to obtain sufiicientlyslow burning delay trains, resides in the fact that slow burning powdersof the type are very difiicult to ignite and when used in delay trainsof small diameter they often fail to burn completely through the delaytrain. The small quantity of powder in the delay train does not evolvesufiicient heat to allow radiation to the metal of the fuze and'stillprovide sufiicient heat to maintain combustion. A further difiilculty isthat while the powders are essen- 'tially gasless, the use of linseedoil or other long been known that when many metals in finely dividedstate are mixed with sulphur such mixtures are readily ignitable and inmany cases burn to yield only solid products, i. e., sulphides I foundby experiment that by of the metal.

In closed systems even small,

It has formulating delay powders so that a reaction be tween metallicchromates and metals-was in'-' volved and at the same time a reactionoccurred between the particular metal used and sulphur, the ignitabilityof such composition was much improved over that of a compositioncontaining only the chromates and a metal. It was found further that thereaction products were entirelS solid and practically no fumes fromvolatilization occurred even at the high temperatures produced by theburning composition if metals having relatively high melting points wereused, e. g., iron, manganese, aluminum, etc.

Examples of compositions which have been especially successful inproviding slow burning, readily ignitable, gasless delay powders are asfollows:

The burning time of a powder column 2" long the above composition is toincrease the ignitability beyond that attainable with chromates andmetals alone. This is attributed to the fact that the compositions havebeen formulated to involve the combination of a series of reactions. Ithas beenfound for example that each of the above chromates as well assilver chromate, calcium chromate and lead chromate not onl react withfinely divided metals such as those listed inthe examples as'wellasmagnesium, aluminum and have a tendency to cease burning in delay trainsof small diameter; on the other hand compositions involving thereactions between the finely divided metals and non-metals are readilyignit-' ible but burn entirely too fast for use as slow burning delaypowders. By combining these reactions, the objections to each separatereaction are overcome and delay powders of improved characteristics overthose previously disclosed by me are obtained, i. e., slow burningcompositions result which readily ignite and when the compositions areloaded in columns of small diameter burn completel through the columns.This is indicated by the data in the examples but additional test datashow that with delay trains of smaller diameters, still slower burningof the powders is obtained, due to reduction in amount of heatliberated, until delays of the order of seconds per inch of powder trainis practicable without ignition failures or failures to burn throughwhen once ignited. Such slow burning is unusual and this characteristicof the new compositions is of much significance since it permits longerdelays in completely obturated fuzes than has been attained heretofore.

The new powders are relatively simple to prepare provided close controlis exercised over the granulation of the ingredients. that the chromatesand the metals be sufficiently fine that they will pass a 250 meshscreen. The powders may be incorporated in the dry state, or wet withwater, carbon tetrachloride or other liquid to reduce the possibility ofaccidental ignition in manufacture. After thorough incorporation, thepowders are granulated by passing through screens or treatment inmechanical granulators commercially obtainable for such purposes. Nobinding agent to assist in granulating has been found necessary althoughsuch might be used if necessary in some special case.

Powders of this type have been found to be non-hygroscopic and ofexcellent stability. They are entirely non-explosive since they evolveno gas upon combustion.

Having thus described the invention, what is claimed as new is:

1. A delay powder which is substantially nongaseous and non-explosiveincluding a metallic chromate, a metal, and a solid non-metallic elementselected from the group consisting of sulphur and phosphorus, saidchromate and said metal being present in a finely divided state.

2. A delay powder which is substantially nongaseous and. non-explosiveincluding a metallic chromate, a metal, and sulphur, said chromate andsaid metal being present in a finely divided state.

3. A delay powder which is substantially nongaseous and non-explosiveincluding 80 per cent barium chromate, 13 per cent manganese, and 7 percent sulphur, said chromate and said manganese being present in a finelydivided state.

4. A non-explosive delay powder formed of a It is desirable mixturecomprising a finely divided metallic chromate, a finely divided metal,and a solid nonmetallic element selected from the group consisting ofsulphur and phosphorus, said mixture being substantially free ofmaterial which forms gaseous products upon combustion.

5. A non-explosive delay powder formed of a mixture comprising a finelydivided alkaline earth chromate, a finely divided metal, and a solidnonmetallic element selected from the group consisting of sulphur andphosphorus, said mixture being substantially free of material whichforms gaseous products upon combustion.

6. A non-explosive delay powder formed of a mixture comprising finelydivided barium chromate, a finely divided metal, and a solid nonmetallicelement selected from the group consisting of sulphur and phosphorus,said mixture being substantially free of material which forms gaseousproducts upon combustion.

7. A non-explosive delay powder formed of a mixture comprising finelydivided barium chromate, a finely divided metal, and sulphur, saidmixture being substantially free of material which forms gaseousproducts of combustion when the mixture burns.

8. A non-explosive delay powder comprising a mixture of a metallicchromate, a metal which reacts with oxygen and a material selected fromthe group consisting of sulphur and phosphorus, the said ingredientsbeing so proportioned that when burned no substantial quantity ofgaseous products will be evolved.

9. A non-explosive delay powder comprising a mixture of barium chromate,manganese, and sulphur, the said ingredients being so proportioned thatwhen burned no substantial quantity of gaseous products will be evolved.

10. A delay powder consisting of 74 to 90 per cent of a metallicchromate, 5 to 24 per cent of a metal which reacts with oxygen, and 2 to7 per cent of a material selected from the group consisting of sulphurand phosphorus.

11. A delay powder consisting of per cent of barium chromate, 13 percent manganese and 7 per cent of sulphur.

12. In the art of improving the ignitability of delay powders includinga metallic chromate and a metal, the improvement which comprisesincorporating in such a delay powder a material selected from the groupconsisting of sulphur and phosphorus.

13. The method of improving the ignitability of a delay powdercomprising an alkaline earth chromate and a metal, the said methodcomprising incorporating in said powder a material selected from thegroup consisting of sulphur and phosphorus,

GEORGE C. HALE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,035,202 Lang Aug. 13, 19121,128,380 Sparre Feb. 16, 1915 1,877,127 Hale Sept. 13, 1932 1,971,502Piccard Aug. 28, 1934 2,157,669 Lazier May 9, 1939 FOREIGN PATENTSNumber Country Date 3,923 Great Britain 1881 24,377 Great Britain 1899

